CVE-2018-0732 : Vulnerability Insights and Analysis

In June 2018, OpenSSL addressed a vulnerability that could lead to a Denial of Service (DoS) attack due to a large Diffie-Hellman (DH) parameter.

Understanding CVE-2018-0732

This CVE entry pertains to a specific vulnerability in OpenSSL that could be exploited by a malicious server to cause a client to hang during a TLS handshake, potentially resulting in a DoS attack.

What is CVE-2018-0732?

During a TLS handshake using a DH(E) based ciphersuite, a malicious server can send an excessively large prime value to the client. This causes the client to spend an extended period generating a key for this prime, leading to a hang until the process completes. This vulnerability can be exploited for a DoS attack.

The Impact of CVE-2018-0732

The impact of this vulnerability is rated as Low according to OpenSSL's severity policy.

Technical Details of CVE-2018-0732

This section provides more technical insights into the vulnerability.

Vulnerability Description

The vulnerability arises during the key agreement phase of a TLS handshake using a DH(E) based ciphersuite, allowing a malicious server to send a large prime value to the client, causing a prolonged key generation process and potential DoS.

Affected Systems and Versions

Affected versions include OpenSSL 1.1.0-1.1.0h and 1.0.2-1.0.2o.

Exploitation Mechanism

A malicious server sends an excessively large prime value to the client during a TLS handshake, leading to a prolonged key generation process and potential DoS.

Mitigation and Prevention

To address and prevent exploitation of this vulnerability, consider the following steps:

Immediate Steps to Take

Update OpenSSL to the fixed versions: 1.1.0i-dev and 1.0.2p-dev.
Monitor for any unusual delays during TLS handshakes that could indicate a potential attack.

Long-Term Security Practices

Regularly update OpenSSL and other security-related software to patch known vulnerabilities.
Implement network monitoring and intrusion detection systems to detect and mitigate potential attacks.

Patching and Updates

Stay informed about security advisories and updates from OpenSSL and other relevant vendors to apply patches promptly.